PREFACE. 



In the "American Journal of Science and Art," A. D. 1847, Prof. 

 J. W. Bailey, of West Point, said: "With the exception of six or 

 eight, I am not aware of any published account of Marine Algce. 

 Of our fluviatile (fresh-water) Algce, I find no published notice, 

 although they appear to have been studied with some care by the 

 indefatigable Schweinitz," and at a little later date he adds: "It 

 appears that to Schweinitz is due the credit of being the first to collect 

 and to study any of our fresh-water Algce." I refer with all the 

 more pleasure to these remarks concerning the late Rev. L. D. von 

 Schweinitz, of Bethlehem, Pa., that he was a friend of my youth, 

 and the first to draw my attention to the study of cryptogamous 

 plants. It is only proper that ample credit should be given to this 

 the first collector of our fresh- water A Igce in this the first monograph 

 published in the United States, on that class of Algce known as 

 DKSMIDS. 



Nearly forty years ago Prof. J. W. Bailey contributed to the 

 "American Journal of Science and Art," two papers, one describing 

 a few new species of Desmids from the Catskill mountains, and the 

 other, "Notes on the Algfe of the United States;" following these 

 'we have "Microscopical Observations made in South Carolina, 

 Georgia, and Florida Smithsonian Institute, A. D. 1850, 50 pp." 

 These observations cover Infusoria and Algce, the latter comprising 

 a list of one hundred and twenty-five species, among which appear 

 a few newly discovered Desmids which are illustrated and described. 



Horatio C. Wood, Jr., M. D., published in 1872, through the Smith- 

 sonian Institute, "A Contribution to the History of the Fresh-Water 

 Algce of North America." In this publication Dr. Wood brought 

 together all the recorded observations that had been made up to that 

 time, in this country and in Europe, upon the Algce of the United 

 States. His list of Algce includes about one hundred and sixty 

 species of Desmids. 



In a collection made by Stephen J. Olney, near Providence, B. I., 

 during the years 1846-48, there were about fifty species of Desmids. 



My first contribution to the literature of the fresh-water Algce 

 appeared in the "Torrey Botanical Bulletin of New York," in 1877, 

 wherein are described thirty Desmids not heretofore found in the 



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